I have a problem with playing and mixing animations using Unity Timelines.
I was looking into this problem for quite some time, but I cannot figure out what is going on.
I created a video that clearly shows a problem I'm experiencing. It was recorded without closing Unity in the meantime.
I start with idle animation and then play the second animation. You can look at one arm of our characters - sometimes the white cloth is appearing.
I performed 8 tests:
TEST 1 - the animation is played from code using SetAnimation() - ok!
TEST 2 - the animation is played from code using SetAnimation() - ok! (never seen any problems using SetAnimation())
TEST 3 - the animation is played using Unity Timelines - the white cloth is appearing - not ok!
TEST 4 - the animation is played using Unity Timelines - the white cloth is appearing - not ok!
----- ADDING A LINE OF CODE AND REFRESH -----
TEST 5 - the animation is played using Unity Timelines - the white cloth is not appearing - ok!
TEST 6 - the animation is played using Unity Timelines - the white cloth is not appearing - ok!
TEST 7 - the animation is played using Unity Timelines - the white cloth is appearing - not ok!
TEST 8 - the animation is played using Unity Timelines - the white cloth is appearing - not ok!
I cannot reproduce this. All I know is that after refreshing assembly for some time it is working ok, but for other people using Unity (e.g. animators), it seems totally random.
I was looking into the Spine Unity Timelines code, but I cannot see any big differences between playing animation from Unity Timelines and from SetAnimation().
This is killing me...

I'm debugging it for quite some time but without any progress.
Do you know where I should look for the solutions?
Thank you!